Lecture 14 Flashcards
Hypothalamus- Pituitary
Your pituitary gland is connected to your hypothalamus through a stalk of blood vessels and nerves (the pituitary stalk). Through that stalk, your hypothalamus communicates with the anterior pituitary lobe via hormones and the posterior lobe through nerve impulses
The Pituitary gland is two glands fused in one
- Posterior pituitary
- Anterior pituitary
Posterior pituitary
is neural tissue and secretes two neuro hormones: vasopressin (antidiuretic hormone or ADH) and oxytocin
Anterior pituitary
is endocrine tissue and secretes six hormones: prolactin, thyrotropin, adrenocorticotropin, growth hormone, follicle stimulating hormone, and luteinizing hormone
Growth hormone (GH): peptide hormone
- GH: 191AA
- Released from anterior pituitary
- Stimulated by GHRH
- Inhibited by Somatostatin
- Acts in liver to stimulate IGF release
IGFR
insulin-like growth factor (acts on liver to secrete IGF-1)- growth- promoting effects on almost every cell in the body
IGFR receptor
tyrosine kinase
Key Concepts for the GH (growth hormone)
- Normal growth
- Anterior pituitary secretes GH
- GH is regulated
Normal growth requires
GH, thyroid hormones, insulin, and sex hormones, Adequate nutrition and no chronic stress
Anterior pituitary secretes GH which Stimulates…
IGF-1 to promote bone and soft tissue growth
GH is regulated by…
Stimulated by GHRH and Inhibited GHIH (aka somatostatin)
Thyroid hormones are made from…
iodine and tyrosine
Gigantism
too much GH in childhood
Acromegaly
too much GH in adulthood
abnormal growth of the hands, feet, and face, caused by overproduction of growth hormone by the pituitary glad
TSH
thyroid stimulating hormone
5 Factors of TSH
- Is a peptide hormone
- It activates G-protein linked membrane receptors acting via Adenylate cyclase
- Stimulates synthesis and activity of enzymes involved in T4 and T3 synthesis
- Activates transcription factors: c-fos, c-myc
- Stimulates thyroid growth
TRH
thyrotropin releasing hormone
Function of Thyroid Hormones
- Metabolic: (metabolic rate, oxygen consumption, heat production, protein degradation, lipolysis)
- Nervous system: (enhances speech, thinking, reflexes)
- Growth and development: (essential in children, works with GH)
- Cardiovascular: (enhances heart rate and contractility; peripheral blood flow, works in part by increasing numbers of beta adrenergic receptors + other proteins)
- Muscular: (too much causes muscle weakness)
The Mechanism of Action of Thyroid Hormones
- T3 and T4 circulate in blood bound to plasma proteins
- T3 more 3-5X more potent than T4
- T4 converted to T3 in target tissues
- Both T3 and T4 bind to nuclear thyroid receptors & alter gene transcription
Graves Disease
(Autoimmune disease) Abnormal antibodies against the TSH receptor are produced.
Hyperthyroidism
(Thyroid hormone ) Causes
- Tumors
- thyroid-stimulating immunoglobulins (Graves’ disease)
Hyperthyroidism
(Thyroid hormone ) Symptoms
goiter, nervousness, insomnia, anxiety, high heart rate, exophthalmos (Graves’ disease), weight loss.
Hyperthyroidism
(Thyroid hormone )
- removal of part of the thyroid gland
- drugs blocking synthesis of T3 and T4 or block conversion of T4 to T3
Hypothyroidism: (Thyroid hormone deficiency) causes
- Under active thyroid gland
Lack of iodine in diet
Hypothyroidism: (Thyroid hormone deficiency) symptoms
goiter, slowed heart rate, slowed speech, fatigue, cold-intolerance, cretinism (infants), stunted growth (infants) and weight gain.
Hypothyroidism: (Thyroid hormone deficiency) treatments
exogenous thyroid hormone T4 (thyroxine)
